A rare form of muscular dystrophy is the result of two unrelated genetic flaws that come together to ultimately produce toxins that damage muscle cells and trigger symptoms.

Facioscapulohumeral muscular dystrophy (FSHD) called type 2 is the third most common form of muscular dystrophy. The first symptoms of the disease usually appear in the form of muscle weakness in the upper body—including in the arms, shoulders, and face.